Abstract 3,3‐Dimethyl selenetane has been polymerized under the influence of different cationic and anionic catalysts. Cationic polymerization led to limited conversions because of the occurrence of a termination reaction between the growing chains and the formed polymer. The obtained polymers had low molecular weights. Anionic polymerization gave polymers with molecular weight up to 35,000. The mechanisms of polymerization are believed to be analogous to the mechanisms proposed for the polymerization of thietanes.